ABSTRACT
The Unified Medical Language System (UMLS) is a long-term research and development effort of the National Library of Medicine, aimed at assisting users in finding information from multiple sources without understanding the intricacies of each particular source. Consisting of three major knowledge sources, a Metathesaurus, a Semantic Network, and a set of lexical processing tools, the UMLS is produced and released twice yearly. Recent efforts have been aimed at expanding coverage in genetics and in clinical vocabularies designed for use in medical record systems. RxNorm, produced and released on a monthly basis, with weekly updates, is an outgrowth of the UMLS, focusing on medication terminology.
